Preparation of amine oxides in non-polar solvent systems

ABSTRACT

SUBSTANTIALLY ANHYDROUS AMINE OXIDES ARE PREPARED BY REACTING A TERTIARY AMINE WITH HYDROGEN PEROXIDE IN A NON-POLAR SOLVENT SYSTEM AND REMOVING WATER FROM THE REACTION MASS AZEOTROPICALLY.

niwd S tes Patent @fice 3,776,959 Patented Dec. 4, 1973 3,776,959PREPARATION OF AMINE OXIDES IN NON POLAR SOLVENT SYSTEMS Joseph S.Stalioraitis and Charles S. Wilhelmy, Chicago, 11]., assignors to AkzonaIncorporated, Asheville, N.C. No Drawing. Continuation-impart ofapplication Ser. No. 686,805, Nov. 30, 1967, now Patent No. 3,558,710,dated Jan. 26, 1971. This application Jan. 25, 1971, Ser. No. 109,574The portion of the term of the patent subsequent to Jan. 26, 1988, hasbeen disclaimed Int. Cl. C07c 85/00 US. Cl. 260-583 D 6 Claims ABSTRACTOF THE DISCLOSURE Substantially anhydrous amine oxides are prepared byreacting a tertiary amine with hydrogen peroxide in a non-polar solventsystem and removing water from the reaction mass azeotropically.

CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part application of our pending application Ser. No.686,805, filed Nov. 30, 1967, now US. Pat. 3,558,710, issued Jan. 26.1971.

The prior art has proposed the preparation of amine oxides from tertiaryamines by reaction with hydrogen peroxide in an aqueous reaction mediumor one that contains polar solvents such as acetone as exemplified bySwiss Pat. No. 177,456. Generally, amine oxides are produced in aqueoussolutions. For many uses the amine oxide containing appreciable amountsof water is undesirable. We do not know of prior methods of obtainingsubstantially anhydrous amine oxides utilizing non-polar solvents.

This invention pertains to a process for the preparation of amine oxideswhich overcomes the above objections. More particularly, the inventionprovides a novel improved process for the preparation and recovery ofamine oxides in the substantially anhydrous state. Even morespecifically, the invention pertains to the production of substantiallyanhydrous amine oxides by reacting a tertiary amine with hydrogenperoxide in a non-polar solvent and simultaneously removing water andsolvent during the reaction by azeotropic distillation.

It is therefore an object of this invention to prepare amine oxides fromtertiary amines while carrying out the reaction in a non-polar solvent.

It is still a further object of this invention to produce amine oxidesby reacting tertiary amines with hydrogen peroxide in non-polar solventand simultaneously removing water and solvent from the reaction vessel.

It is another further object of this invention to produce substantiallyanhydrous amine oxides by reacting a tertiary amine with hydrogenperoxide in non-polar solvent and thereafter removing water from thereaction mass azeotropically.

Another object of this invention is to prepare substantially anhydrousamine oxides by reacting a tertiary amine such asdi-(2-hydroxyethyl)cocoamine with hydrogen peroxide -in a non-polarsolvent such as xylene with the simultaneous removal of water from thereaction mass by azeotropic distillation.

It is still a further important object of this invention to improve themethod of producing amine oxides wherein a tertiary amine is reactedwith hydrogen peroxide by carrying out the reaction in non-polarsolvent, azeotropically removing the water from the reaction mass andthereafter recovering amine oxide.

These and other further important objects will become apparent from thedisclosure and from reference to the specific, detailed examples.

Generally, the method of the invention comprises fluidizing a tertiaryamine with a suitable amount of non-polar solvent and thereafter addinga peroxide such as hydrogen peroxide over a period of time in order toobtain reaction and conversion of the tertairy amine to the amine oxide.It is generally preferred to heat the amine-solvent mixture prior tohydrogen peroxide addition. During the reactionor after the reaction iscompleted,.water obtained.

from the solution of hydrogen peroxide as well as that obtained as areaction product is removed along with the non-polar solvent byazeotropic distillation thereby obtaining substantially anhydrous amineoxide as the end product. Generally speaking, the azeotropicdistillation conditions will vary with the type of non-polar solventused, but in each case it is important to the process that thetemperature be such that it is below the decomposition point of thespecific amine oxide formed.

Specifically, a tertiary amine is added to a reaction vessel, such as around bottomed flask or reactor with substantial amount of head space,about 25 to 50% being preferred and 32 to 35% especially preferred.Depending upon the molecular weight of the tertiary amine, there isadded a suffiicent amount of non-polar solvent to fluidize the amine toinsure proper contact with the later added hydrogen peroxide. Theamine-non-polar solvent composition is heated and hydrogen peroxide isadded with stirring. The peroxide may be added in aqueous solution formwherein the hydrogen peroxide concentration is about 1 to weightpercent, the preferred range being about 30 to 50 weight percent. Thoseskilled in the art will recognize that the only limitations of hydrogenperoxide concentration are safety ones.

In a preferred form of the invention, the reaction mass is maintained ata temperature sufiicient to promote reaction during hydrogen peroxideaddition and sufficient to azeotrope water from the system. Because thereaction involved is exothermic, it may be necessary to cool thereaction mass and maintain temperatures below the decompositiontemperature of the formed amine oxide. Ordinarily, the temperatureshould not be over about C., about 40 to 100 C. is suitable and about 60to 90 C. is preferred.

After a period of time it may be necessary to add additional solvent inorder to maintain fluidity of the reaction mass mixture. Aftercompletion of the reaction and after azeotropic distillation, it will befound that amine oxide is recovered in the substantially anhydrousstate, that is no more than about 1 to 2 weight percent water present.Reaction times may vary but ordinarily about A to 10 hours is suitable.

It is desirable to continuously azeotrope water and return substantiallydry solvent to the reactor. In such case, the solvent-water mixtureremoved by azeotropic distillation is treated to separate the solventfrom the water and the solvent is recirculated into the reactor. Otherobvious expedients will be readily observable to those skilled in theart.

Suitable amines for conversion to amine oxides include the tertiaryamines in which the groups directly bonded to the amino nitrogen atomare hydrocarbon groups and those in which the groups directly bonded tothe amino nitrogen atom are substituted hydrocarbon in character. Thehydrocarbon groups bonded to the amino nitrogen atom may be aliphatic oraromatic in character. The aliphatic groups may be of a branched chainor a straight chain configuration or they may be cyclic in character;they may be saturated or they may be olefinically unsaturated. Thealiphatic groups may be the same or dilferent.

Tertiary amines particularly suitable for the practice of this inventioninclude those of the formulae:

R is of the group C -C alkyl and alkenyl; R is of the group of CH:methyl, (GIhCH O H and (OHzHO).H

Other amines as well as processes of preparing these amines may be foundin US. Pat. No. 3,398,197 and US. Pat. No. 3,494,962, the disclosures ofwhich are hereby incorporated by reference.

The types of amine oxides formed according to the present inventioninclude those of the following formulae:

wherein R, R and R" are identified above.

R as identified above may be alkyl and alkenyl groups including hexyl,heptyl, octyl, nonyl, decyl, hendecyl, dodecyl, tridecyl, tetradecyl,pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl,docosyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, hendecenyl, dodenyl, rid c yl, t tradece yl, pentadecenyl, hexadecenyl, heptadecenyl,octadecenyl, nonadecenyl, eicosenyl, docosenyl, octadecadienyl,octadecatrienyl and mixtures thereof such as found in fats and oilsincluding coconut, soybean, tallow and tall oil.

The alkylene group R" may contain from 2 to 6 carbon atoms; that is thealkylene group may be dimethylene, trimethylene, tetramethylene,pentamethylene or hexamethylene and their branched chain isomers such as2-methyl-l,3-propylene, 1-methyl-1,3-propylene and 1- methyl ethylene.One especially preferred embodiment is the presence of the trimethylenegroup.

The hydrogen peroxide employed may be in the form of an aqueous solutioncontaining from about 10% to about by weight of hydrogen peroxide.Particularly useful are the commercially available aqueous solutionscontaining from about 35% to about 70% by weight of hydrogen peroxide.It is preferable that the highest practical concentration of hydrogenperoxide consistent with safe handling be employed to minimize Watercontent since water is subsequently removed. For the same reason, whileit is quite feasible to employ stoichiometric quantities of the hydrogenperoxide relative to the amine reactant, that is, one mole of hydrogenperoxide per mole of amine, it is desirable that the hydrogen peroxidebe present in the reaction zone in an amount somewhat in excess of thetheoretical amount. The excess of hydrogen peroxide need not exceed andin most cases an excess of hydrogen peroxide of about 10 to 50% will befound suflicient for the desired purpose.

The oxidation of the amine can be carried out at atmospheric,superatmospheric or subatmospheric pressure, as may be desirable. In thegreat majority of cases, it will be found that operation atsubstantially atmospheric pressure will be found to be most convenient.Preferred temperatures for effecting the reaction are of the order offrom about 40 C. to about 100 C. In most cases, little advantage will beobtained through the use of temperatures in excess of about 100 C. ascompared to the use of somewhat lower temperatures. As a matter of fact,temperatures over 100 C. may be detrimental as the amine oxide formedwill decompose. Under these conditions of temperature and pressure,reaction times of the order of from about one-half hour to about tenhours will be found suflicient to effect the desired reaction tocompletion.

Suitable non-polar solvents for use in this invention include aromatichydrocarbons, aliphatic hydrocarbons and chlorinated hydrocarbons.Specific examples include, ut are not limited to, benzene, toluene,xylene, high boiling mineral spirits, kerosene, carbon tetrachloride,dichloroethane, hexane, heptane and the like solvents, of which the artis well aware. Mixtures of the foregoing solvents may be used ifdesired.

The amount of the non-polar solvent used is not critical, but sufiicientnon-polar solvent should be employed to fluidize the amine reactant andto remove contained water from the reaction system. If the solvent isrecycled, lesser total amounts of solvent are required. Generally theweight of non-polar solvent used is from less than the weight of theamine reactant to several times the weight of the amine. Usually, notmore than about five to ten times the weight of the amine reactant ofnonpolar solvent need be used. In most cases a weight of nonpolarsolvent of from about 1 toabout 4 times the weight of the amine reactantis most convenient.

In conducting the reaction of the amine and the hydrogen peroxide, it isdesirable that the reactants be brought together slowly. In most cases,it will be found most desirable that the amine reactant be mixed withthe non-polar solvent, and the hydrogen peroxide added slowly to thestirred reaction mixture, the reaction temperature being controlled :byheating or cooling as necessary. The order of mixing may be different,however, addition of the hydrogen peroxide to the amine is the preferredtechnique, since it permits better control of the reaction andminimization of undesired by-products.

6 EXAMPLE 111 Using the same general procedure as Example I, thefollowing reaction system was used:

5 Ethomeen C/ 12 402 Xylene 349 64 wt. percent H 0 aqueous solution 82The following Table II shows the time sequence and analysis of thereaction system.

TABLE II A nalysis, wt. percent Free amino Amine oxide H: H20

amine and the amount of amine oxide may be determined.

The foregoing analysis procedure is set forth at Analytical Chemistry,vol. 34, p. 1849, 1962.

EXAMPLE I To 574 g. di-(Z-hydroxyethyl) cocoamine (Ethomeen C/ 12") in areactor was added 456 g. toluene. To the amine-solvent mixture was added163 g. of 46 wt. percent hydrogen peroxide solution, while stirring thereaction mass, over an addition period of 1 /2 hours at a temperature of70-76 C. Conversion of amine to amine oxide took place over a period ofabout 4-5 hours during which the temperature of the reaction mass wasabout 76 -84 C. Azeotropic distillation of the resultant reaction massat 83 C. at atmospheric conditions over a period of about 5 hoursyielded a product in solvent having the following analysis by weightpercent:

Added ml. xylene EXAMPLE IV 267.5 gms. (0.25 mole) of coco (15 molepropylene oxide adduct) tertiary amine (Propomeen C/25) 90% pure wasmixed with 1,000 gms. 1,2-dichloroethane in a 5 liter reaction flaskequipped with an efiicient stirrer, thermometer, and condenser. Afterthe mixture was heated to about C., 26 gms. of 50 wt. percent hydrogenperoxide was added dropwise. The hydrogen peroxide addition was adjustedso the reaction temperature was maintained at about to C. After thehydrogen peroxide was added, the reactor contents were digested at about68 C. for four hours. The water was distilled out by azeotroping withdichloroethane at about 72 C.

The product was analyzed and found to contain, in addition to solvent:

Weight percent 45 Amine oxide 12.0 Amine oxide 45.2 Unreacted tertiaryamine 5.1 Free amine 1.4 Water 0.6 H 0 .6 Hydrogen peroxide 0.12

EXAMPLE II Using the same general procedure as indicated in Example Isubstituting the reactants as follows:

EXAMPLE V G. Di (2 hydmXyethy1) cocoamine 573 Th pr re of ample IV wasfollowed with the Benzene 457 following reaction system:

64 Percent H202 soln 117 Di-(hydrogenated tallow) methylter- Thefollowing Table I shows the time sequence for the tiary amine 96% pure23 gms. (1 mole). above described reaction system illustrating thesimul- H 0 (50 wt. percent in H O) 68 gms. taneous distillation andoxidation aspect of the invention: Cyclohexane 1,060 gms.

TABLE I Analysis Temp., 0. H202 H20 Amine Free Gardner Time Pot Vaporin, ml ofi, ml. oxide amine H10: H20 color Reflux starts Blightthickening of reaction mass After four hours an additional 240 gms. ofhydrogen peroxide, as used above, was added. The mixture was digestedfor six hours and water-cyclohexane as azeotroped out at 65 C.

The product was analyzed and found to contain, in addition to solvent:

Weight percent 8 EXAMPLE VIII Amine oxide 21.5 vessel. Unreactedtertiary amine 7.4 The following Table III shows the time sequence forWater 0.7 10 the above described reaction system together with analy-Hydrogen peroxide 0.12 sis of the contents of the reaction vessel.

TABLE III Analysis weight ercent Temp., C.- p Pressure, Amine Time hoursPot Vapor mm. Hg Amine oxide H; E20

1 Start vacuum.

The amine oxide was di-(hydrogenated tallow) methyltertiary amine oxide.

EXAMPLE VI The procedure of Example IV was followed with the followingreaction system:

N-tallow trimethylene diamine (3 moles ethylene oxide adduct) tertiaryamine (Ethoduomeen TD/l3) 135.3 gms. (0.3 mole). H 0 (50 wt. percent inH O) 60.0 gms. (0.9 mole). Hexane 750.0 gms.

Amine oxide 11.2 Unreacted tertiary amine 1.5 Water Trace Hydrogenperoxide Trace The amine oxide was N-tallow trimethylene diamine (3moles ethylene oxide adduct) tertiary amine oxide.

EXAMPLE VII The procedure of Example IV was followed with the followingreaction system:

H 0 (50 wt. percent in H O) 13.9 gms. (4.26 moles). Dimethyloctadecylamine 320.0 gms. (4.7 moles). Heptane 705.0 gms.

The mixture reacted in the same maner as Example VI with the waterazeotroped out at about 96 C. vapor temperature. 210 gms. of water weredistilled.

The product was analyzed and found to contain, in addition to solvent:

Weight percent Amine oxide 35.2. Unreacted tertiary amine 13.5. Water1.5 approx. Hydrogen peroxide Trace.

The amine oxide was dimethyloctadecy amine oxide.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave been set forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:

1. In the process for producing amine oxides wherein a tertiary amineselected from the group consisting of di-2-l1ydroxy-ethyl coco amine,coco tertiary amine, di- (hydrogenated tallow) methyl-tertiary amine,dimethyl octadecyl tertiary amine and N-tallow trimethylene diaminetertiary amine is reacted with hydrogen peroxide, the improvementcomprising carrying out the reaction in a nonpolar solvent selected fromthe group consisting of benzene, toluene, xylene, 1,2-dichloroethylene,cyclohexane, heptane and mixtures thereof, and azeotropically removingwater from the reaction mass at a temperature below the decompositiontemperature of the amine oxide formed in said reaction.

2. .The process of claim 1 wherein said azeotropic removal of water iscarried out during said reaction.

3. The process of claim 1 wherein the solvent removed azeotropicallyfrom said reaction system with water is separated from said water andre-circulated to said reaction system.

4. The process of claim 1 wherein said amine oxide is recovered insubstantially anhydrous state.

5. The process of claim 1 wherein said reaction is carried out at atemperature of about 40 to 100 C.

6. The process of claim 1 wherein said reaction is carried out at atemperature of about 60 to C.

References Cited UNITED STATES PATENTS 3,558,710 1/1971 Stalioraitis eta1. 260-584 R LEWIS GO'ITS, Primary Examiner R. L. RAYMOND, AssistantExaminer US. Cl. X.R.

260570.5 P, 570.8 R, 583 R, 583 P, 584 R, 584 B

